At Malloys by the river near Martinez. We haven't been there since it was called Barrancas de Alvear but I've heard that the food has improved enormously.
I'll check in tomorrow with a full report.
https://www.google.com.ar/maps/place/MALLOY%C2%B4S/@-34.4793263,-58.4845804,17z/data=!3m1!4b1!4m5!3m4!1s0x95bcb1991cc6a745:0x2ba301b3e6002d39!8m2!3d-34.4793263!4d-58.4823917